Glass fiber reinforced polystyrene article and process therefor



United States Patent 3,441,466 GLASS FIBER REINFORCED POLYSTYRENE ARTICLE AND PROCESS THEREFOR Samuel Sterman, Williamsville, and James G. Marsden,

Tonawanda, N.Y., assignors to Union Carbide Corporation, a corporation of New York No Drawing. Filed Feb. 1, 1966, Ser. No. 523,879 Int. Cl. B29c 17/04; 1332b 17/04 US. Cl. 161-93 6 Claims This invention is directed to glass-reinforced polysty- Iene.

Polystyrene resin is a thermoplastic material of construction which is used in a large number of applications such as toys, housewares, toilet articles, packaging, name plates, refrigerator parts, wall tile, and many others. However, normally polystyrene has low strength, poor heat resistance, and it crazes readily. Such shortcomings can be mitigated to a certain extent by the incorporation within the polystyrene resin of strengthening materials such as glass in fibrous form.

It has now been found that further improvement in the physical properties of polystyrene can be achieved by treating styrene resin, with certain chemical compounds. Accordingly, it is the principal object of this invention to provide as a material of construction polystyrene reinforced by fibrous glass and exhibiting materially enhanced physical properties while retaining its thermoplastic properties.

A further object of this invention is to provide a method for enhancing the physical properties of glass-reinforced polystyrene resin.

Still other objects will become obvious to one skilled in the art upon reference to the ensuing specification and the claims. I

The objects of this invention are achieved by an article of manufacture which is a thermoplastic composite of fibrous glass, polystyrene, and an organofunctional alkyltrialkoxysilane which can be an (epoxycycloalkyl) alkyltrialkoxysilane or an (acryloxy)alkyltrialkoxysilane.

The above article of manufacture possessing the enhanced physical properties can be prepared by (1) providing a fibrous glass substrate, (2) by treating this substrate with the aforementioned organofunctional alkyltrialkoxysilane, (3) then intimately contacting the treated glass substrate with the polystyrene resin, and (4) thermoforming the resulting composite at a temperature below the decomposition temperature of the resin and the silane.

Polystyrene is a thermoplastic resin derived from homopolymerization of styrene. The resin is substantially fully polymerized, is chemically inert, and contains no apparent reaction sites. The resin may be thermoformed over and over again without undergoing further cure or hardening. Any residual unsaturation remaining in polystyrene after the polymerization is purely incidental and does not afiect the thermoplastic nature of the resin.

The crux of the present invention is the selection of the proper organofunctional silane for the treatment of the fibrous glass employed for reinforcement. This selection must be carried out with great care since an improper choice will work to the detriment of the physical properties of the ultimate article. Furthermore, considerable research into the reaction mechanisms involved has failed to cast light on the observed phenomena and the prediction of the performance of a particular organofunctional silane in the selected resin system, even on the basis of observed performance of silanes having closely related organofunctional groups, is virtually impossible.

Two groups of organofunctional silanes have been found to materially enhance the physical properties of polystyrene resin reinforced with fibrous glass: the (epoxy- "ice cycloalkyl)alkyltrialkoxysilanes and the (acryl0xy)alkyltrial-koxysilanes.

Illustrative of the former group are beta-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, beta-(3,4 epoxycyclohexyl propyltriethoxysilane, beta- (4,5-epoxycycloheptyl) ethyltrimethoxy silane, beta-(2,3-epoxycyclohexyl)butyltripropoxysilane, and the like. In this connection it should be noted that the use of gamma-(glycidoxypropyl)trimethoxysilane fails to give the desired enhancement in the physical properties.

Illustrative of the latter of the aforementioned organofunctional silanes that are suitable for the practice of the present invention are gamma-(methacryloxy)propyltrimethoxysilane, beta- (acryloxy)ethyltriethoxysilane, delta (methacryloxy butyltrimethoxysilane, gamma- (acryloxy) propyltributoxysilane, and the like.

In order to be suitable for the purposes of the present invention the glass must be fibrous; however, any form of fibrous glass can be employed. Suitable are woven cloth, chopped mat, continuous strand mat, chopped strand, roving, woven roving, and the like. Powdered glass is not suitable.

The fibrous glass can be treated, i.e., sized, with the organofunctional silane in any convenient manner. The silane can be applied to the glass fibers at the extrusion bushing as the fibers are produced or the sizing can be carried out by means of an aqueous solution of the proper silane into which the glass fibers are dipped and subsequently dried. In the latter instance the corresponding hydrolyzate is deposited on the substrates.

It will be apparent to one skilled in the art that the materials actually deposited on glass fabric from aqueous silane solution in the examples appearing below are hydrolyzates rather than the silanes as such. These hydrolyzates are siloxanes e.g., epoxycycloalkylsiloxane (such as beta-(3,4-epoxycyclohexyl)ethylsiloxane) and acyloxyalkylsiloxanes (such as gamma-glycidoxypropylsiloxanes). During hydrolysis, the epoxy rings of the epoxycycloalkylsilanes may open to produce hydroxycycloalkylsiloxanes.

The loading of the silane on the glass fibers must be sufiicient to enhance the fiexural strength of the ultimate thermoformed article. While for practical applications the loading is usually expressed in terms of weight percent, based on the weight of the treated glass fibers, it must be noted that the minimum loading requirement may vary depending on the surface area of the particular glass fibers that are employed. When fibrous glass having a surface area of from about 0.1 to about 0.2 square meter per gram is employed effective silane loading can range from about 0. 01 to about 5 weight percent, based on the weight of the treated fiber. Preferably the silane loading is in the range from about 0.1 to about 0.75 weight percent.

The silane-treated fibrous glass and the polystyrene resin are brought in intimate contact with each other in any convenient manner and then thermoformed. The term thermoforming as used herein and in the appended claims is taken to mean the transformation of the resinsilane-glass composite into useful shapes by means of heat and/ or pressure. Illustrative thermoforming processes are molding, extrusion, hot calendering, casting, vacuum forming, and the like.

Several methods of achieving intimate contact between the treated fibrous glass and the polystyrene resin are illustrated by the examples below. Still other methods include the utilization of polystyrene film or sheet and the preparation of a dry laminate having alternating plies of fibrous glass and polystyrene which is then molded, the admixture of chopped silane-treated glass fibers with warm or hot, fluid polystyrene resin in a mechanical mixer prior to extrusion, the treating of continuous, silane-treated roving with a solution of the polystyrene resin in a suitable to treat the glass fabric. Due to the solubility charactersolvent, the calendering of the polystyrene resin onto a istics of this silane it was applied to the glass fabric from treated glass cloth or mat, and the like. a 75-25 water ethanol solution. The flexural strengths of The following examples further illustrate the present this composite under the same conditions as recited in invention. 5 Example I are reported in Table I, below.

EXAMPLE I EXAMPLE III i i g etfiect on the Another silane treated glass reinforced polystyrene S reng a rem PO g yrene i g; 1 composite was prepared as described in Example I except gq g g {8 g i g. (a gg c o avuig a gamma-glycidoxypropyltrimethoxysilane was used to E 2 ounces i g g treat the glass fabric. The flexural strengths of this comyar i X an s an PIC S per Square mo at} posite under the indicated conditions are given in Table a breaking strength of 375 x 350 pounds per square men; I below the weaving size having been burned off in a heat clean- EXAMPLE IV ing operation) without a silane treatment and woven glass reinforcement treated with gamma-methacryloxy- Another sllane treated glass reinforced polystyrene compropyltrimethoxysilane. The silane was applied to the glass P it Was prepared as described in Example I except in the following manner: vinyltris(beta-methoxy-ethoxy)silane was used to treat the An aqueous treating both containing about one weight glass fabric. The flexural strengths of this composite under percent gamma-methacryloxypropyltrimethoxysilane was the indicated conditions are given in Table I, below.

prepared by adding the silane to water adjusted to pH 20 TABLE I 3.5-5 with acetic acid and gently stirring until the silane silane Flexuml Strength psi XHH hydrolyzed resulting in a clear colorless solution. Ten inch wide stri s of the woven glass fabric were passed through 9 the treat d solution, dried at room temperature, and then Composition percent Dry Wet (93 placed in an oven for two and one-half minutes at 135 C. 25 gontrol 3 The glass fabric picked up about one-half of its weight FQQY; 5 4&4 3L0 2&9 of the treating solution, and after evaporation of the solgi -gg fgggfii figggl 0 5 42 8 33 5 2&3 vent there remained a coating on the glass fabric equivavjnyl t is(beta methoxy. lent to about 0.5 weight percent of the silane, based on f the weight of the fabric. 30 t ifdi1 bli oZ sil2frie i R 0.5 27. 5 22. 5 15.

The silane treated glass fabric was then impregnated with polystyrene resin by passing the silane treated glass From the data in the foregoing Table it is readily fabric through a wt.-percent solution of polystyrene apparent that a substantial enhancement of the flexural resin in toluene, allowing most of the toluene to evaporate strength was achieved using an (alcryloxy)alkyltrialkoxysat room temperature, and then driving off the last traces ilane or an (epoxycyclocloalkyl)alkltriolkoxysilane of solvent by heating the treated fabric at 135 C. for whereas in contradistinction thereto silanes with similar 1 /2 hours. The treated fabric at this point contained about organofunctional groups (c.f.: vinyl vs. acryloxy, glycid- 75 wt.-percent resin based on the weight of the glass oxy vs. epoxycyloalkyl) failed to achieve a material fabric, increase in flexural strength.

The polystyrene-impregnated, silane treated glass fab- EXAMPLE V ric was then cut into 10" x 10 squares and 11 plies of A laminate prepared in accordance with the method set this material placed in a press preheated to about 177 forth in Example II was evaluated for its electrical prop- C. and pressed to 0.125 inch stops. This composite was erties. The results are reported in Table II below.

TABLE II Dielectric constant, Dissipation factor, Volume resistivity, Dielectric strength,

1,000 cycles/sec. 1,000 cycles/sec. ohm/cm. volts/mil.

Dry Wet Dry Wet Dry Wet Dry Wet Polystyrene-i-uuizreated glass 3. 5 13. O 0. 070 0. 850 10 215 16 Polystyrene-l treated glass 3.7 3.8 0.002 0. 00s 10 10 216 216 l The laminates were immersed for about 16 hours in water at about C. and tested at room temperature.

2 Very low.

molded for 20 minutes under these conditions, the press The above data indicate that the polystyrene laminates cooled, and the composite removed. A composite apwith glass cloth treated with beta-(3,4-epoxycyclohexyl) proximately 0.125 inch thick and having a resin content of ethyltrirnethoxysilane possess remarkably superior elecabout -"P Was Obtainedtrical properties inasmuch as such properties are not A second composite was prepared by the same proceaffected by an extended soaking of the laminate in water.

dure except untreated woven glass fabric was used as the 0 We Claim, gfg f g 5 5 g g 5 5 2 33 1. A method for reinforcing substantially fully poly- 4 1/ H 1/ H g t f p b th F; d merized thermoplastlc polystyrene resin wh1ch comprises x 2 X 8 were Cu mm o composl es an e 1) providing a fibrous glass substrate, (2) treating the flexural strength determined according to ASTM method D-7990-61. Specimens from each composite were divided into three groups. Group 1 was tested at room temperature, Group 2 at room temperature after the spicemens had been immersed in water at 50 C. for 16 hours and Group 3 was tested at 93 C. The fiexural strengths are glass substrate with an organofunctional alkyltrialkoxysilane which is a member of the group consisting of (epoxycycloalkyl)alkyltrialkoxysilane and (acryloxy) alkytrialkoxysilane so as to deposit thereon said silane or a hydrolzate thereof, (3) intimately contracting the treated glass substrate with the polystyrene resin, and

given in Table I below.

(4) thermoforming the resultlng composlte at a tem- EXAMPLE H perature below the decomposition temperature of the resin Another silane treated glass reinforced polystyrene and the silane; the amount of silane deposited on the glass composite was prepared as described in Example I except fiber being sufiicient to enhance the flextural strength of beta(3,4-epoxycyclohexyl)ethyltrimethoxysilane was used the thermoformed composite.

2. The method in accordance with claim 1 wherein the organofunctional alkyltrialkoxysilane is beta-(3,4-epoxycyclohexyl)ethyltrimethoxysilane or the corresponding hydrozate thereof.

3. The method in accordance with claim 1 wherein the organofunctional alkyltrialoxysilane is gamma-methacryloxy-propyltrimethoxysilane or the corresponding hydrolylyzate thereof.

4. An article of manufacture which is a thermoplastic composite of fibrous glass, polystyrene, and an organofunctional alkyltrialkoxysilane selected from the group consisting of (epoxycycloalkyl)alkyltrialkoxysilane and (acryloxy)alkyltrialkoxysilane or a corresponding hydrolyzate thereof.

5. An article of manufacture in accordance with claim 4 wherein the organofunctional alkyltxialkoxysilane is beta-(3,4-epoxycylohexyl)ethyltrimethoxysilane or the corresponding hydrolyzate thereof.

6. An article of manufacture in accordance with claim 4 wherein the organofunctional alkyltrialkoxysilane is gamma-rnethacryloxypropyltrimethoxysilane or the corresponding hydrolyzate thereof.

References Cited UNITED STATES PATENTS 3,306,800 2/1967 Plueddernann 16l-193 ROBERT F. BURNETT, Primary Examiner.

W. J. VAN BALEN, Assistant Examiner.

US. Cl. X.R. 

4. AN ARTICLE OF MANUFACTURE WHICH IS A THERMOPLASTIC COMPOSITE OF FIBROUS GLASS, POLYSTYRENE, AND AN ORGANOFUNCTIONAL ALKYLTRIALKOXYSILANE SELECTED FROM THE GROUP CONSISTING OF (EPOXYCYCLOALKYL)ALKYLTRIALKOXYSILANE AND (ACRYLOXY)ALKYLTRIALKOXYSILANE OR A CORRESPONDING BYDROLYZATE THEREOF. 